Conventionally, a door opening/closing device for a double folding door that closes an opening when the two door panels are in the unfolded state, and opens the opening when the door panels are in the folded state includes a support shaft that foldably joins the two door panels, and a torsion spring that is coaxially disposed on the support shaft.
Then, the door panels are opened against the resistance of the elastic force of the torsion spring, and the door panels are automatically closed by the elastic force of the torsion spring.
However, in a conventional door opening/closing device, a torsion spring having a single coil portion is used, so, structurally, the torsion spring must be used so that when the door is opened, the coil portion is wound open, and when the door is closed, the coil portion is wound tight.